Merge tag 'topic/atomic-fixes-2014-12-17' of git://anongit.freedesktop.org/drm-intel...

Yeah a pull for one patch is a bit overkill but I started to assemble the
various patches for 3.20 in a branch for atomic props/ioctl and didn't
realize that this bugfix here at the beginnning of the branch should be in
3.19 (because msm is using the helpers arleady). So if you'd merge we'd
have it twice or or I need to shuffle branches again. Can do if you want.

* tag 'topic/atomic-fixes-2014-12-17' of git://anongit.freedesktop.org/drm-intel:
  drm/atomic: fix potential null ptr on plane enable